#app{
  width: 800px;
  height: 400px;
  border: 1px solid #ccc;
  margin: 30px auto;
}
*{
  margin: 0;
  padding: 0;
}
.body{
  height: 350px;
}
.head{
  height: 50px;
  border-bottom:1px solid #ccc;
  position: relative;
}
li{
  list-style: none;
}
.head ul {
  height: 100%;
  display: flex;
  align-items: center;
}

.head li {
  width: 100px;
  text-align: center;
  border-right:1px solid #ccc;
  height: 100%;
  line-height: 50px;
  cursor: pointer;
  position: relative;
}

.head .select{
  background-color: #f3f3f3;

}
.content-item{
  font-size: 50px;
  height: 100%;
  display: none;
}
.show{
  display: block;
  display: flex;
  align-items: center;
  justify-content: center;
}
.add{
  position: absolute;
  right: 10px;
  top: 0px;
  font-size: 30px;
  display: flex;
  height: 100%;
  align-items: center;
  cursor: pointer;
}

.close {
  position: absolute;
  right: 0 ;
  top: 0;
  display:block;
  height: 20px;
  width: 20px;
  line-height: 20px;
  color: red;
}
.close:hover{
  background-color: #aaa;
}